This invention relates generally to read/write head sliders or transducers. More particularly this invention relates to read and write transducers that are physically separated from each other with the read transducer located a greater distance above a disc than the write transducer.
Rotating disc magnetic recording systems typically employ magnetic head transducers which glide over the magnetic disc media on a cushion of air. The mounting or support structure which carries the transducers are termed xe2x80x9csliders.xe2x80x9d Sliders have air-bearing surfaces that are propelled off the surface of moving media by boundary air which moves with the media disc. The air-bearing surface of a slider is aerodynamically designed to glide on the boundary air due to a pattern of raised rails and recesses which establish the xe2x80x9cfly heightxe2x80x9d of the slider. Read/write transducers are mounted on the air-bearing side of the slider, facing the moving media.
A slider assembly typically includes the ceramic slider and associated read/write heads, a support flexure arm, interconnection wires between the heads and external signaling devices, and any associated mounting hardware. That assembly is mounted on an arm which is movable over the surface of a rotating magnetic disc to position the slider adjacent selected tracks on the disc. Disc drives usually employ multiple discs which rotate together, spaced apart from one another on a single spindle. One slider assembly is provided for each magnetic recording surface in a disc drive.
In magnetic disc drive data storage devices, digital data are written to and read from a thin layer of magnetizable material on a surface of one or more rotating discs. Write and read operations are performed through write and read transducers. The slider and transducers are sometimes collectively referred to as a head, and typically a single head is associated with each disc surface. When the read transducer is a magnetoresistive (MR) type sensor, the combination of the slider and the transducer are frequent referred to as a MR head. The head is selectively moved under the control of electronic circuitry to any one of a plurality of circular, concentric data tracks on the disc surface by an actuator device. Each slider body includes an air bearing surface (ABS). As the disc rotates, the disc drags air beneath the ABS, which develops a lifting force that causes the head to lift and fly above the disc surface.
It is desirable for the air-bearing surface of a slider to fly as close to the media as possible, without actually physically touching the media. Read/write signal strength is dependent on the spacing between the thin layer of magnetizable material on the surface of the rotating disc and the read/write head. A close spacing between the thin layer of magnetizable material on the surface of the rotating disc and the read/write head substantially improves the transducer""s performance.
It is also important for the spacing between the slider and media disc to be invariant from the innermost to the outermost diameter data tracks. The fly height of the read/write head above the media should be the same at the inner diameter, mid diameter and outer diameter of the disc. This is difficult since the media travels faster as the read/write head moves from the inner diameter towards the outer diameter of the disc.
Thermal effects are exaggerated by slider flying heights that are very close to the media. Thermal effects include the natural tendency of materials to expand when heated, quantified by a temperature coefficient of thermal expansion more conveniently called a thermal expansion coefficient. Materials with higher coefficients expand more in response to a given temperature increase. When materials having different thermal expansion coefficients are contiguous and integral, their differing expansion when heated leads to elastic deformations and elastic restoring forces in both of the materials. This effect is seen on the slider most often near the transducers that are located proximate to one another. Due to differences in material thermal expansion properties, the transducers are usually encapsulated in insulating material that differs from the material of the slider body. The insulating material expands at a different rate than the material of the slider body in response to a given temperature increase. As current flows into the transducer, the material surrounding the transducer is heated and expands due to Ohm""s law. The expansion of the material surrounding the transducer forms a protrusion directed towards the disk. This unwanted effect is known as thermal pole tip protrusion. Thus, reduced flying heights increase the need to take thermal expansion and thermally induced elastic deformation into account.
In operation, the MR element (MRE) of the head can come into contact with asperities on the surface of the disc. This is particularly true in proximity type heads where the inductive write transducer comes into frequent contact with the surface of the disc. Potentially, this contact between the MRE and asperities can cause data written to a particular location on the disc to be lost. Immediately after contact with an asperity, the heat generated by the contact changes the resistive properties of the MR sensor. As a result, the corresponding signal read by the MR head is distorted by a voltage spike and subsequent decay, sometimes causing the data stored near the asperity to be unrecoverable. The voltage spike in the read back signal is frequently referred to as a xe2x80x9cthermal asperity,xe2x80x9d while the defect on the disc is referred to as an xe2x80x9casperityxe2x80x9d. However, since one is indicative of the other, the two terms are frequently used interchangeably. Since disc media contain asperities, proximate MR sensors have to be designed to prevent the MR sensor from physically touching the media and creating thermal asperities in the read back signal. Thus, these MR sensors are designed to fly higher above the media to prevent contact with the media and as a result of the greater fly height, these sensors also have decreased signal strength.
Therefore, there is a need for improved read/write slider design that will reduce slider fly height above the media, maintain a constant fly height across the disc, and minimize both thermal pole tip protrusion and thermal asperities.
According to a first aspect of the present invention there is provided a read/write head that includes a slider flying above a rotating disc. The slider has an upper side, a lower side, and a trailing edge face. The lower side faces the rotating disc and is separated from the rotating disc by an air gap. A write transducer is located on the lower side of the slider and is a first height above the rotating disc. A read transducer is located on the lower side of the slider and is a second height above the rotating disc. The second height is greater than the first height.
According to another aspect of the invention there is provided a disc drive system that includes a magnetic recording disc and a slider flying above the disc. The slider has an upper side, a lower side, and a trailing edge face. The lower side faces the rotating disc and is separated from the disc by an air gap. A write transducer is located on the lower side of the slider and is a first height above the rotating disc. A read transducer is located on the lower side of the slider and is a second height above the rotating disc. The second height is greater than the first height. The disc drive system includes an actuator for moving the slider across the magnetic recording disc and a detection circuitry electrically coupled to the slider for detecting changes in resistance of the slider caused by magnetic fields from the magnetically recorded data.
The above, as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.